1. Field of the Disclosure
The present disclosure relates to a display device, and more particularly, to a display device with an integrated touch screen.
2. Discussion of the Related Art
A touch screen is a kind of input device that is installed in an image display device, such as a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an electroluminescence device (EL), an eletrophoretic display (EPD), etc., to allow a user to input predetermined information by pressing (or touching) a touch sensor in the touch screen while viewing the image display device.
Touch screens are classified into an add-on type, an on-cell type and an in-cell type depending on a structure of a touch screen installed in a display device. An add-on type touch screen is manufactured separately from a display device and is attached on an upper substrate of the display device. An on-cell type touch screen comprises elements directly formed on an upper substrate of a display device. An in-cell type touch screen is built in a display device such that the display device has a thin thickness and improved durability.
However, a display device with an add-on type touch screen has disadvantages of thick thickness and low visibility from low brightness. Although it has a thinner thickness than the display device with an add-on type touch screen, a display device with an on-cell type touch screen has disadvantages of increased total thickness, manufacturing processes and manufacturing costs because of driving electrodes, sensing electrodes, and an insulating therebetween for the touch screen.
On the other hand, a display device with an in-cell type touch screen, which may be referred to as a display device with an integrated touch screen, is able to improve durability and to have a thin thickness, thereby solving the problems of the display device with an add-on type touch screen and the display device with an on-cell type touch screen. The display device with an in-cell type touch screen may be classified into optical type and capacitive type. The capacitive type may be subdivided into self capacitance type and mutual capacitive type.
A display device with a mutual capacitance in-cell type touch screen includes a common electrode divided into driving electrodes and sensing electrodes such that mutual capacitance is generated between the driving electrodes and the sensing electrodes and measures a change in the mutual capacitance due to a touch of a user, thereby detecting the touch. A display device with a self capacitance in-cell type touch screen includes a common electrode divided into a plurality of parts such that the plurality of parts are used as touch electrodes and capacitance is generated between the touch electrodes and an input of a user, and a change in the capacitance due to a touch of the user is measured, thereby detecting the touch.
The display device with a self capacitance in-cell type touch screen will be described in detail with reference to FIG. 1.
FIG. 1 is a view of a display device with a self capacitance in-cell type touch screen according to the related art.
In FIG. 1, the display device with a self capacitance in-cell type touch screen of the related art includes a panel 10, a display driver IC (integrated circuit) 20, and a touch IC 30. The panel 10 includes m driving electrodes 13 and m signal lines 14 and is divided into a display area 11 and a non-display area 12. The display driver IC 20 applies a common voltage or a touch scan signal to the m driving electrodes 13 through the m signal lines 14. The touch IC 30 generates the touch scan signal to provide the display driver IC 20 with the touch scan signal and receives touch sensing signals according to the provided touch scan signal to detect a location of a touch input of a user. Here, the m driving electrodes 13 are formed in the display area 11.
In the self capacitance type touch screen of the related art, touch sensitivity varies depending on an area of the electrodes contacting the touch input of the user. Namely, the touch sensitivity is proportional to the area of the electrodes contacting the touch input.
Therefore, the touch sensitivity in a peripheral region of the display area 11 is lower than the touch sensitivity in an inner region of the display area 11, which is surrounded by the peripheral region of the display area 11.
In the self capacitance type touch screen of the related art, the location of the touch input is detected by calculating signals (change in the capacitance) generated between the touch input of the user and the electrodes using algorithm. The larger the area of the electrodes contacting the touch input is, the more the signals (change in the capacitance) are. If algorithm calculation for detecting the location of the touch input is made using more signals, relatively high touch sensitivity may be obtained.
By the way, when there is a touch input in the peripheral region of the display area 11, a part of the touch input may exist in the non-display area 12. For example, when a single touch input contacts or overlaps a boundary between the display area 11 and the non-display area 12, the touch input exists in both the display area 11 and the non-display area 12.
However, since electrodes are not formed in the non-display area 12, the signals according to the touch input cannot be generated in the non-display area 12, and signals for the algorithm calculation are insufficient. Therefore, the touch sensitivity when the touch input exists in the peripheral region of the display area 11 is lower than the touch sensitivity when the touch input exists in the inner region of the display area 11.
For instance, when an touch input is applied to a region “a” or applied to a region “b,” average touch sensitivity may be obtained because the touch input exists in the display area 11, and when an touch input is applied to a region “c” or a region “d,” touch sensitivity lower than the touch sensitivity in the region “a” or the region “b” may be obtained because the touch input exists in the display area 11 and the non-display area 12, where the electrodes for generating signals according to the touch input are not formed.
More particularly, the touch sensitivity in the region “c” is lower than the touch sensitivity in the region “a” and the region “b,” and the touch sensitivity in the region “d” is lower than the touch sensitivity in the region “c.” This is why the touch sensitivity is proportional to the area of the electrodes contacting the touch input.
In the self capacitance type touch screen of the related art, a solution to solve the low touch sensitivity in the peripheral region of the non-display area 11 has been sought for.